Istraživalo se je na ribnjačarstvu »Draganići« tijekom uzgojne sezone god. 1990., u 8 pokusnih ribnjaka pojedinačne veličine 0,1 ha-1. Uzgajao se konzumni šaran u polikulturi s bijelim i sivim glavašem i bijelim amurom, s ukupnom količinom nasađenih riba 3.250 ind×h-1 (77% šarana, 23% biljojedi). Istraženo je djelovanje gnojidbe i različitog prihranjivanja na ribe s obzirom na: prinos i prirast ribe, individualnu masu riba, gubitke, hranidbeni koeficijent, Fultonov i Klarkov koeficijent uhranjenosti. Istražilo se i biokemijsko stanje u pojedinim ribnjacima.
Utvrđena su jaka osciliranja pojedinih biokemijskih parametara u tijeku uzgojne sezone, napose količine kisika čije su vrijednosti povremeno bile ispod poželjne razine.
Ukupni prirast riba iznosio je u prosjeku 703 kg ha-1 (kontrola bez gnojidbe, prihranjivanje riba žitaricama), 1.302 kg ha-1 (gnojidba, prihranjivanje riba žitaricama) i 2.573 kg ha-1 (bez gnojidbe, prihranjivanje riba bjelančevinama životinjskog porijekla). Rezultate ilustriraju tablice 3, 4 i 5.
Gubici šarana bili su slični u svim varijantama pokusnih ribnjaka, ipak nešto veći u kontrolnoj, nepovoljnoj varijanti. Prosječna individualna masa šarana bila je uz gnojidbu veća 30%, a uz prihranjivanje bjelančevinastim briketima (20% bjelančevina) 154%.
Hranidbeni je koeficijent u gnojenoj varijanti bio 26% niži, a uz prihranjivanje bjelančevinama 13%. Fultonov i Klarkov koeficijent uhranjenosti bio je sličan u svim ribnjacima, s iznimkom boljih vrijednosti Fultonova koeficijenta u varijanti koja je prihranjivana bjelančevinama i koje su bile statistički opravdane (p<0001). U toj je varijanti utvrđena i najveća dužina i težina šarana (p<OOOl).
Dodatni prirast riba na račun biljojeda iznosio je 92 kg ha-1 (var I), 404 kg ha-1 (var II) i 650 kg ha-1 (var III), bez nepovoljna djelovanja na prirast šarana.This research was carried out on 8 experimental fish-pounds with individual sizes of 0,1 ha-1 on fish farm Draganići during 1990 culturing season. Carp was reared under conditions of polyculture with total stock density 3250 ind × ha-1. (77 % carp, 2500 ind × ha-1 ; 23% -- 250 ind × ha-1 each species of herbivorous fish – silver carp, bighead, grass carp). The influence of fertilization and different feeding of fish was researched through these parameters: yield and increment of fish, individual weight, losses, food conversion, Fultons and Clark’s coefficient of carp. The hydrochemical conditions in individual pounds where researched too (tabl 2).
The total increment of fish was 703 ind × ha-1 (I variant, without fertilization, feeding of carp with cereals), 1302 ind × ha-1 (variant II, fertilization, 500 kg × ha-1 NPK 17: 8: 9, feeding with cereals) and 2537 kg × ha-1 (variant III, without fertilization, feeding carp with pellets containing 20% protein of animal origin). The increment of carps was 611.4; 897.8 and 1923.5 kg × ha-1 resp. The results of production are shown on tables 3, 4 and 5.
The losses of carp were similar in all variants of fish-pounds (tabl. 4).
The average individual weight of carp was 30% bigger in the fish pond with fertilization, and 154% in fish pond with feeding carp with pellets containing 20% protein of animal origin in compare to control variant 1.
Food conversion was lower for 26% in the variant which was fertilized, and for 13% in the variant fed with protein pellets, in compare to control variant l.
The Fulton\u27s and Clark\u27s condition coefficient of carp was similar in all experimental ponds except in the variant III. In this variant the Fulton\u27s condition coefficient was significantly better (P<O,OOOl) as well as the length and weight of carp (P).
The presence of herbivorous fishes in this polyculture enlarged the total increment of fishes for 92 kg\u27ha-1 (variant I), 404 kg\u27ha-1 (variant II) and 650 kg\u27ha-1 (variant II!), without an inhibitory effect on the growth rate of carp
